Grinding machine with wheel dress compensating apparatus

ABSTRACT

A grinding machine having a feed nut rotatably journalled in a wheel head, a lead screw rotatably journalled in a bed being threadedly engaged with the feed nut, a worm wheel coaxially mounted on the feed nut and a worm rotatably journalled in the wheel head being meshed with the worm wheel is provided with compensating means connectable with the worm to rotate the same and thereby advance the wheel head for compensating for grinding wheel dressing and a motor for rotating the worm in an opposite direction to retract the wheel head for exchanging grinding wheels when the wheel in use has become too worn.

[ Feb. 112, 1974 GRINDING MACHINE WITH WHEEL DRESS COMPENSATING APPARATUS [75] Inventors: Ichizo Kakumu, Nagoya; Teruyuki Ito, Kariya, both of Japan [73] Assignee: Toyoda Kolki Kabushiki Kaisha,

Aichi-ken, Japan [22] Filed: Oct. 15, 1971 [21] Appl. No.: 189,584

[30] Foreign Application Priority Data Oct. 16, 1970 Japan 45-103868 [52] US. Cl. 5l/l65.87 [51] Int. Cl B24b 49/18 [58] Field of Search 51/65 R, 165.87, 165.88

[56] References Cited UNITED STATES PATENTS 2,931,145 4/1960 Hill a 5l/165.88

3,627,490 12/1971 Asano ..51/165.87

Primary Examiner-Harold D. Whitehead Attorney, Agent, or FirmObl0n, Fisher, Spivak, Mc- Clelland & Maier 57 ABSTRACT A grinding machine having a feed nut rotatably journalled in a wheel head, a lead screw rotatably journalled in a bed being threadedly engaged with the feed nut, a worm wheel coaxially mounted on the feed nut and a worm rotatably joumalled in the wheel head being meshed with the worm wheel is provided with compensating means connectable with the worm to rotate the same and thereby advance the wheel head for compensating for grinding wheel dressing and a motor for rotating the worm in an opposite direction to retract the wheel head for exchanging grinding wheels when the wheel in use has become too worn.

6 Claims, 5 Drawing Figures i l l' 64 I 38 11111 I 1111 /7 a 24 g 2/ 2; 2a

DU? 32 P LL 35 PATENTEDFEB 12 law amt GRINDING MACHINE WITH WHEEL DRESS COMPENSATING APPARATUS BACKGROUND OF THE INVENTION The present invention relates generally to grinding machines and more particularly to an improved apparatus for compensating for wheel dress of the grinding wheels in such machines.

Since the dressing of a grinding wheel operates to reduce its radius, it is necessary to subsequently advance the dressed grinding wheel an amount equal to the reduction in its radius in order to compensate for the dressing operation performed thereon. When a grinding wheel eventually becomes worn down to the point where it must be replaced by a new and larger wheel, it therefore is necessary to retract the wheel head which rotatably supports the grinding wheel so that the new wheel may be properly positioned thereon. The wheel head can be retracted manually by rotating a handwheelwhich is arranged f o r r otatinga lead screw engaged with the wheel head in the properdirection. Since such operations, however, are very laborious and require a great amount of time, automatic performance of the operation is a highly desirable attribute.

In a prior art grinding machine, the lead screw is engaged with a nut secured to the wheel head and is appropriately connected with a feed shaft which extends to the front of the machine and is there provided with a hand wheel. An apparatus for compensating for wheel dress and a feed mechanism for advancing the wheel head during a grinding operation are connected with the feed shaft by way of respective clutches. In such machines, if a motor were provided for driving the feed shaft to automatically retract the wheel head, the hand wheel on the end of the feed shaft would be rotated together with the feed shaft at a very rapid speed. This would be very dangerous for a machine operator, and thus cannot be adopted.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a grinding machine having an apparatus which is not only capable of advancing the wheel head to compensate for wheel dress but also capable of automatically retracting the wheel head in safety.

Another object of the present invention is the provision of an apparatus for automatically moving the wheel head of agrindingmachine beyond the feeding range thereof normally effected by the feed mechamsm.

The foregoing and other objects are obtained in accordance with one aspect of the present invention through the provision of a grinding machine having a feed nut rotatably joumalled in a slidable wheel head, a lead screw rotatably joumalled in the main support of the machine being threadedly engaged with the feed nut, a worm wheel coaxially mounted on the feed nut and a worm rotatably joumalled in the wheel head meshingly engaging the worm wheel. Compensating means are connectable with the worm for rotating the same in one direction to advance the feed nut and the wheel head a predetermined amount and thereby compensate for the dressing of a grinding wheel and a motor is connected with the worm for rotating the same in an opposite direction to retract the feed nut and the wheel head a predetermined amount for permitting a new larger grinding wheel to be substituted for a worn wheel. In addition, a separate lead screw rotating means is provided which permits moving the feed nut independently of the worm drive through rotation of the lead screw but prevents lead screw rotation while the compensating means and the motor are being operated.

BRIEF DESCRIPTION OF THE DRAWINGS Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description of a preferred embodiment of the present invention when considered in connection with the accompanying drawings in which:

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to FIG. 1 thereof, a grinding machine is shown.

having a bed 10 on which a work table 11 is slidably mounted. The work table 11 carries a head stock 12 and a tail stock not shown, between which a workpiece W is rotatably supported. A base 13 is fixedly mounted on the bed 10 and a wheel head l4is slidably mounted thereon for movement in a path perpendicular to the movement of the slidable work table 11. The wheel head 14 rotatably supports a wheel spindle which carries at one end thereof a grinding wheel 15. The spindle 60 carries at its other end a belt pulley 61 that is connected by one or more belts 62 to a pulley 63 secured to a rotary shaft of an electric motor 16 also mounted on the wheel head 14.

A bracket 17 is secured to the underside of the wheel head 14. A feed nut 19 having a worm wheel portion 18 is rotatably joumalled in needle bearings 64, 64 fixed to the bracket 17 and is prevented from moving in the axial direction by thrust bearings 65, 65. A lead screw 20 threadedly engaged with the feed nut 19 is disposed in parallel relation with the path of movement of the wheel head 14. The lead screw 20 is rotatably connected to a piston 21 at its rear end, but is refrained from moving axially relative to the piston 21 by thrust bearings 66, 66. The piston 21 is slidably received in a cylinder 24 bored in a support 23 which is secured to the base 13. The front end of the lead screw 20 is confronted with a stop 22 rotatably supported by the base 13. Dogs 26 and 27 are adjustably mounted on a rod 25 secured to the piston 21 for actuating respective limit switches 28 and 29 attached to the support 23.

A gear 30 is fixed to the middle portion of the lead screw 20 and meshingly engages an idler gear 31 rotatably mounted on the support 23. The idler gear 31 meshingly engages a gear 32 affixed to one end of a feed shaft 33 which is rotatably supported by the bed and extends to the front of the machine. Feed shaft 33 is fixedly connected to a hand wheel, not shown, at the front end thereof and is connected with a feed mechanism through a conventional clutch 81. The feed mechanism includes a pinion 82 connected with the feed shaft 33 through the clutch 81, a rack 83 engaged with the pinion 82 and a hydraulic cylinder connected with the rack 83 for causing reciprocation of the same. The lead screw is therefore rotated by the hand wheel or the feed mechanism through gears 32, 31 and 30. A nut 67 threadedly engaged with the lead screw 20 is held in spline engagement with the feed nut 19 and a spring 34 is interposed therebetween to eliminate backlash.

As shown in FIG. 2, a worm shaft 37 is rotatably journalled in bearings 68, 68 fixed to the bracket 17 and is restrained from moving in an axial direction by thrust bearings 70, 70. A worm 38 of the worm shaft 37 is meshed with the worm wheel 18 of the feed nut 19. A housing 39 is attached to the side surface of the wheel head 14 and rotatably supports a shaft 40 through bearings 71, 71 fixed therein. Movement of the shaft 40 is restricted in the axial direction only by thrust bearings 72, 72. The shaft 40 is aligned with the worm shaft 37 and is connected therewith by a conventional universal joint 41. A ratchet wheel 42 is keyed to the shaft 40 at its left end portion and is capable of being engaged by a ratchet 43. The ratchet 43 is pivotally mounted on a rocking member 45 and is resiliently urged toward the ratchet wheel 42 by a spring 58. The rocking member 45 is keyed to a sleeve 47 which is rotatably mounted in a casing 46 secured to the housing 39. The shaft 40 coaxially extends through the sleeve 47. The rocking member 45 has a pinion 44 formed thereon that meshingly engages a rack 48 formed on a piston rod 50 of a piston 73, shown in FIG. 4. A cylinder 49 is secured to the casing 46 and slidably receives the piston 73.

As shown in FIGS. 2 and 5, an adjusting ring 52 is rotatably mounted on the casing 46. A connecting portion 74 of the adjusting ring 52 extends to the inside of the casing 46 through an elongated slot 75 therein. A block portion 53 projects from the connecting portion 74 in the axial direction and confronts the side surface of the ratchet wheel 42. The ratchet 43 is broader than the ratchet wheel 42 in width and hangs over the block portion 53. Since the ratchet 43 runs on the block portion 53 at its rest position, the engagement of the ratchet 43 with the ratchet wheel 42 is usually released. A cap 54 secured to the casing 46 prevents the adjusting ring 52 from coming off the casing 46. A set screw 80 threadedly engaged with the adjusting ring 52 abuts a boss projecting from the cap 54 and sets the adjusting ring 52 at the adjusted position.

As shown in FIGS. 2 and 3, a bevel gear 55 is keyed to the middle portion of the shaft 40 and is meshed with a bevel gear 56 attached to a rotary shaft of an electric motor 57 which is secured to the housing 39. The electric motor 57 may be a hydraulic motor or a conventional pulse motor.

A conventional dressing device 76, shown in FIG. 1, is mounted on a guide 77 secured to a cover 78 fixed to the wheel head 14 and is slidable transversely across the peripheral surface of the grinding wheel 15. A

dressing tool 79 of the dressing device 76 is movable toward and away from the surface of the grinding wheel 15.

The grinding machine and the apparatus for compensating for wheel dress which is constructed according to the present invention as described above, operates in the following manner. After the workpiece W is suitably supported between the spindle head 12 and the tail stock, a starting button, not shown, is pushed. A solenoid-operated valve 35, shown in FIG. 1, is then shifted to its alternate state in which pressurized fluid is supplied to the rear chamber of the cylinder 24, whereupon the piston 21 is caused to move in the forward direction and the wheel head 14 is thereby advanced toward the workpiece at a rapid speed through the lead screw 20 and the feed nut 19. When the forward end of the lead screw 20 approaches the position where it abuts the stop 22, the limit switch 28 is actuated by the dog 26. Thereafter, the rack 83 of the feed mechanism is advanced by the hydraulic cylinder and the feed shaft 33 is rotated through the engagement of the rack 83 with the pinion 82 connected to the shaft 33. Since the rotation of the feed shaft 33 is transmitted to the lead screw 20 by way of the gears 32, 31 and 30, the wheel head 14 is now moved toward the workpiece W at a slow speed through the engagement of the lead screw 20 with the feed nut 19. Thus, the workpiece W is ground by the advancing grinding wheel 15. When the grinding operation is completed, the rack 83 of the feed mechanism is retracted by the hydraulic cylinder and the feed shaft 33 and the lead screw 20 is rotated in the opposite direction, whereby the wheel head 14 is moved away from the workpiece W. Concurrently, the solenoid-operated valve 35 is shifted to the state shown in FIG. 1 in which the pressurized fluid is supplied to the front chamber of the cylinder 24. This moves the piston 21 in the backward direction and retracts the wheel head 14 until the limit switch 29 is actuated by the dog 27.

After several grinding operations have been carried out, the dressing device 76 may be moved transversely across the surface of the grinding wheel 15 so that the grinding wheel 15 is dressed by the dressing tool 79 a predetermined amount. When the dressing operation has been completed and the dressing device 76 has been returned to its rest position, the dressing tool 79 is fed by a predetermined dressing amount in the direction of the grinding wheel 15 for the next dressing operation. At the same time a solenoid-operated valve 51, shown in FIG. 4, is shifted to its alternate state in which pressurized fluid is supplied to the right chamber of the cylinder 49. The piston 73 is therefore moved in the leftward direction. Since the rack 48 of the piston rod 50 is moved in the same direction, the rocking member 45 is rotated in the clockwise direction through the engagement of the rack 48 with the pinion 44. The ratchet 43 is swung by the rocking member 45 and is slipped off the block portion 53 to engage the ratchet wheel 42 for rotating the same. The rotation of the ratchet wheel 42 is transmitted to the worm 38 through the shaft 40, the universal joint 41 and the worm shaft 37. The worm wheel 18 is rotated by the worm 38 and consequently the feed nut 19 is rotated. Since at this time rotation of the lead screw 20 is prevented by the feed mechanism, the feed nut 19 is advanced by its rotation and the wheel head 14 is moved therewith toward the workpiece W. The range of the rotation of the feed nut 19 can be varied by changing the position at which the ratchet 43 slips off the block portion 53 by rotating the adjusting ring 52. The range of the rotation of the feed nut may be selected so that the amount of movement of the wheel head 14 is equal to the dressing amount, and the adjusting ring 52 when adjusted is then fixed to the cap 54 by the set screw 80. Thus, the reduction of the diameter of the grinding wheel 15 due to the dressing operation can be readily compensated by preselected movement of the wheel head 14.

Thereafter, the solenoid-operated valve 51 is shifted back to its original position shown in FIG. 4 in which pressurized fluid is supplied to the left chamber of the cylinder 49 so that the piston 73 is moved to the right. The rocking member 45 is rotated in the counterclockwise direction in accordance with the movement of the rod 50 of piston 73 and the ratchet 43 is therefore rotated in the same direction being run up onto the block portion 53 is returning to its rest position.

When the grinding wheel 15 has been worn out, it must be replaced by a larger one. Since the wheel head 14 is, as mentioned above, advanced relative to the lead screw for compensating for the dressing operation, it is necessary to first retract the wheel head 14 before making the exchange. A push button, not shown, is pushed to energize the electric motor 57 for retracting the wheel head 14. The bevel gear 56 is rotated by the electric motor 57 and the shaft 40 is rotated in the reverse direction through the engagement of the bevel gear 55 keyed thereto with the bevel gear 56. The worm wheel 18 is rotated in accordance with the rotation of the shaft 40 and the feed nut 19 is therefore rotated in the reverse direction so as to rapidly retract the wheel head 14. The wheel head 14 actuates a limit switch secured to the base 13,.not shown, at its retracted position for de-energizing the electric motor 57. Thus the wheel head 14' may be positioned at its retracted position. Since the ratchet 43 is running on the block portion 53, it does not obstruct the reverse rotation of the shaft 40. Following the wheel head retraction, the worn-out grinding wheel may easily be exchanged for a new, larger grinding wheel.

Moreover, according to the grinding machine of the present invention, the wheel head can be advanced or retractedby the motor corresponding to the diameter of the workpiece, when workpieces vary in diameter by an amount such that the difference of the diameters is beyond the moving range of the wheel head-normally effected by the feed mechanism.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A grinding machine comprising:

a bed: I

work support means mounted on said bed for supporting a workpiece;

a wheel head slidably mounted on said bed for rotatably supporting a grinding wheel thereon;

a dressing device mounte'don said wheel head for dressing the grinding wheel;

a lead screw rotatably journalled in said bed;

a feed mechanism for rotating said lead screw;

a feed nut rotatably journalled in said wheel head and being threadedly engaged with said lead screw;

a worm wheel coaxially mounted on said feed nut;

a worm journalled in said wheel head and meshingly engaging said worm wheel;

compensating means connected with said worm to rotate it for compensating the position of said wheel head by an amount equal to the dressing amount, said compensating means including a ratchet wheel being in connection with said worm and a ratchet engageable with said ratchet wheel only upon its actuation for rotating said worm in one direction; and

a rotary motor secured to said wheel head and being connected with said worm for rotating the same in the other direction, said rotary motor being rotated in said one direction by said compensating means and upon energization thereof reversing the rotation of said worm for returning said wheel head to an original starting position thereof.

2. A grinding machine as set forth in claim 1, wherein a first bevel gear is fixedly mounted on a shaft connected with said worm and is meshed with a second bevel gear secured to a rotary shaft of said rotary motor.

3. A grinding machine as set forth in claim 2, wherein said compensating means comprises:

a rocking member rotatably mounted on said wheel head;

drive means for rotating said rocking member; and

a ratchet pivoted on said rocking member and being urged toward said ratchet wheel.

4. A grinding machine as set forth in claim 3, wherein said compensation means comprises a block means adjustably mounted on said wheel head for releasing the engagement of said ratchet with said ratchet wheel.

5. In a grinding machine have a bed, workpiece supporting means mounted on the bed, a wheel head slidably mounted on the bed for supporting a grinding wheel, a lead screw rotatably journalled in the bed, a feed nut threadedly engaged with the lead screw being connected with the wheel head for sliding the same upon movement thereof axially of the lead screw to move the grinding wheel relative to the workpiece and a dressing device on the wheel head for dressing the grinding wheel, the improvement comprising;

compensating means releasably connectable with said feed nut for rotating the same in one direction about said lead screw to move said whee] head a predetermined amount toward said workpiece to compensate the reduction of the diameter of said grinding wheel every time a dressing operation is performed thereon;

a worm wheel on said feed nut;

a worm journalled in said wheel head and meshingly engaging said worm wheel;

a rotary motor fixedly connected with said feed nut for rotating the same in an opposite direction about said lead screw, said rotary motor being rotated in said one direction by said compensating means and upon energization thereof reversing the rotation of said worm for returning said wheel head to an original starting position thereof, for perrnitting replacement of a worn grinding wheel; and

means for selectively rotating the lead screw and for preventing rotation thereof during the operation of being biased toward engagement with said ratchet wheel; blocking means adjustably mounted on said wheel head for releasing the engagement of said ratchet and said ratchet wheel to thereby disconnect said compensating means from said feed nut; and means for adjusting said blocking means to vary the range of rotation of said feed nut. 

1. A grinding machine comprising: a bed: work support means mounted on said bed for supporting a workpiece; a wheel head slidably mounted on said bed for rotatably supporting a grinding wheel thereon; a dressing device mounted on said wheel head for dressing the grinding wheel; a lead screw rotatably journalled in said bed; a feed mechanism for rotating said lead screw; a feed nut rotatably journalled in said wheel head and being threadedly engaged with said lead screw; a worm wheel coaxially mounted on said feed nut; a worm journalled in said wheel head and meshingly engaging said worm wheel; compensating means connected with said worm to rotate it for compensating the position of said wheel head by an amount equal to the dressing amount, said compensating means including a ratchet wheel being in connection with said worm and a ratchet engageable with said ratchet wheel only upon its actuation for rotating said worm in one direction; and a rotary motor secured to said wheel head and being connected with said worm for rotating the same in the other direction, said rotary motor being rotated in said one direction by said compensating means and upon energization thereof reversing the rotation of said worm for returning said wheel head to an original starting position thereof.
 2. A grinding machine as set forth in claim 1, wherein a first bevel gear is fixedly mounted on a shaft connected with said worm and is meshed with a second bevel gear secured to a rotary shaft of said rotary motor.
 3. A grinding machine as set forth in claim 2, wherein said compensating means comprises: a rocking member rotatably mounted on said wheel head; drive means for rotating said rocking member; and a ratchet pivoted on said rocking member and being urged toward said ratchet wheel.
 4. A grinding machine as set forth in claim 3, wherein said compensation means comprises a block means adjustably mounted on said wheel head for releasing the engagement of said ratchet with said ratchet wheel.
 5. In a grinding machine have a bed, workpiece supporting means mounted on the bed, a wheel head slidably mounted on the bed for supporting a grinding wheel, a lead screw rotatably journalled in the bed, a feed nut threadedly engaged with the lead screw being connected with the wheel head for sliding the same upon movement thereof axially of the lead screw to move the grinding wheel relative to the workpiece and a dressing device on the wheel head for dressing the grinding wheel, the improvement comprising; compensating means releasably connectable with said feed nut for rotating the same in one direction about said lead screw to move said wheel head a predetermined amount toward said workpiece to compensate the reduction of the diameter of said grinding wheel every time a dressing operation is performed thereon; a worm wheel on said feed nut; a worm journalled in said wheel head and meshingly engaging said worm wheel; a rotary motor fixedly connected with said feed nut for rotating the same in an opposite direction about said lead screw, said rotary motor being rotated in said one direction by said compensating means and upon energization thereof reversing the rotation of said worm for returning said wheel head to an original starting position thereof, for permitting replacement of a worn grinding wheel; and means for selectively rotating the lead screw and for preventing rotation thereof during the operation of said compensating means and said rotary motor.
 6. In the grinding machine of claim 5, wherein said compensating means comprises: a ratchet wheel mounted on a shaft extending from said worm; a rocking member rotatably mounted on said wheel head; means for rotating said rocking member; a ratchet pivotably mounted on said rocking member being biased toward engagement with said ratchet wheel; blocking means adjustably mounted on said wheel head for releasing the engagement of said ratchet and said ratchet wheel to thereby disconnect said compensating means from said feed nut; and means for adjusting said blocking means to vary the range of rotation of said feed nut. 